Flow controller



Sept. 1, 1964 R. L. CHENAULT FLOW CONTROLLER Filed Oct. 30. 1961INVENTOR. E R0) L. CHE/VAUL T y WXZEzZZZ A Horney I 500 I000 PressureDifferenr/alpsi United States Patent M 3,146,798 FLOW CIINTROLLER RoyI... Chenault, Seneca, Pa, assignor to United htates Eteei Corporation,a corporation of New .Iersey Fiied (let. 319, 1961, Ser. No. 148,513Claims. (Ci. 138-44) This invention relates to an improved controllerfor limiting the rate at which fluid can flow through a hydraulic orpneumatic system.

Although my invention is not thus limited, my controller is particularlyuseful as a governor applied to a hydraulically operated subsurfacemotor and pump combination used in an oil well. conventionally suchcombinations include a hydraulic motor and a reciprocating pump locatednear the bottom of a well. A stream of power oil is pumped down the welltubing at a substantially constant pressure to drive the motor. Exhaustpower oil from the motor subsequently returns to the surface, eitherblending with oil pumped from the well or via a separate return line. Inpractice the load on the pump may be removed quite suddenly, as when thewell pumps oiI, or the load may be removed during part of a strokebecause of free gas in the oil. When the pump is thus unloaded and losesresistance, the motor tends to run at a high speed which results indamage to the mechanism. Because of the compressibility of oil andelasticity of the tubing, a large amount of energy may be stored in thepower oil. Hence any control means located at the surface is ineffectivefor preventing damage. Nevertheless my controller may have applicationelsewhere for overcoming analogous problems in a hydraulic or pneumaticsystem.

An object of my invention is to provide an improved controller whicheifectively limits the flow rate of fluid therethrough to a safe maximumdespite loss of resistance to flow downstream of the controller.

A further object is to provide an improved controller which achieves theforegoing purpose, yet is of simple compact construction of dimensionsto be installed near the bottom of a well and free of moving parts.

A more specific object is to provide an improved controller which hasthe foregoing characteristics and includes a housing, a restriction inthe housing for increasing the velocity of a stream of fluid as it flowstherethrough, and means for creating turbulence in the stream at thepoint of increased velocity.

In accomplishing these and other objects of the invention, I haveprovided improved details of structure, preferred forms of which areshown in the accompanying drawing, in which:

FIGURE 1 is a longitudinal sectional view of one form of controllerconstructed in accordance with my invention;

FIGURE 2 is a longitudinal sectional view showing a modification;

FIGURE 3 is a longitudinal sectional view showing another modification;

FIGURE 4 is a longitudinal sectional view showing still anothermodification; and

FIGURE 5 is a graph showing a set of curves to demonstrate how mycontroller limits the rate of flow therethrough to a definite maximum.

FIGURE 1 shows one form of my controller which comprises a housing 10, aconnector 12 at the upstream end of the housing, and a two-part venturidevice 13, 14. When I use this controller with a hydraulically operatedsubsurface motor and pump combination, I attach the downstream end ofhousing to the inlet of the motor as close to the motor as possible, andI attach connector 12 either directly to the power oil tubing of aninserttype pump, or to a fishing neck and oil inlet nipple of a3,146,798 Fatented Sept. 1, 1964 pump that may be inserted and removedhydraulically. Housing 10 has an internal shoulder 15 against which thedownstream part 14 of the venturi device rests. I may place an annulargasket 16 on the other face of the downstream part 14 and place theupstream part 13 of the venturi device on this gasket. Optionally thegasket can be omitted and the upstream part 13 can bear directly againstthe downstream part 14. The connector 12 is threadedly engaged with theupstream end of housing 10 and bears against the face of the upstreampart 13 to hold the venturi device in position.

The venturi device has walls which form a tapered inlet passage 17, athroat 18 and a flared outlet passage 19. The upstream part 13 has aplurality of intake passages 2t) spaced in a circle around the inletpassages 17. The face of the upstream part 13 adjacent the downstreampart 14 has an annular groove 21. The space within this groove forms achamber which communicates with passages 20. The upstream part also iscut away adjacent throat 18 to form an annular connecting passage 22which affords communication between the chamber and throat.

In operation, a stream of fluid enters the upstream end of housing 10,flows through passage 17, throat 18 and passage 19, and dischargesthrough the downstream end. Normally this fluid is under substantiallyconstant pressure upstream of the housing, but the pressure downstreamrnay drop. Loss of downstream pressure of course increases the pressuredifference between the two ends of the housing. As long as the pressuredifference remains within a predetermined range, the rate at which thestream flows through the housing varies almost directly with thepressure difference. Whenever the loss of downstream pressure increasesthe pressure difference above a critical value, the rate of flow throughthe housing levels off, and thereafter remains substantially constantdespite any further increase in the pressure difference. This result isattained by fluid flowing through passages 20, chamber 21 and passage 22and impinging on the high-velocity stream at throat 18, where the streamhas a greater velocity than it has through the remainder of the housing.

FIGURE 2 shows a modification in which a bypass 25 replaces the intakepassages 20. I use this form of controller in accessible locations wherecompactness is less essential. The controller comprises a housing 26, aconnector 27 threadedly engaged with the downstream end of the housing,a two-part venturi device 28, 29 and an annular plug 30 threadedlyengaged with the housing upstream of the venturi device. The housingcontains an internal flange 31. I fix the upstream part 28 of theventuri device between plug 30 and flange 31, and I fix the downstreampart 29 between connector 27 and flange 31. The venturi device has atapered inlet passage 32, a throat 33 and a flared outlet passage 34.The space between its two parts 28 and 29 forms an annular chamber 35and an annular connecting passage 36, which affords communicationbetween the chamber and throat, similar to corresponding parts inFIGURE 1. I connect one end of the bypass 25 into the housing upstreamof the venturi device, and the other end to the housing opposite chamber35. The bypass contains a valve 37, which I can adjust to regulate thevalue at which the flow rate levels off. Preferably I also connect anoutside source 38 of fluid with the bypass as an alternate means forsupplying fluid to the venturi throat. This source is equipped with avalve 39.

FIGURE 3 shows a modification in which upstream and downstream orificeplates 42 and 43 replace the venturi device. This form comprises ahousing 44 and upstream and downstream connectors 45 and 46 threadedlyengaged with opposite ends of the housing. The housing contains aninternal flange 47. I fix the upstream orifice plate 42 betweenconnector 45 and flange 4-7 and I fix the downstream orifice plate 43between connector 46 and flange 47. The orifice plates provide arestricted orifice 48 for increasing the fiuid velocity. The spacebetween the orifice plates forms an annular chamber 49 and an annularconnecting passage 53 which affords communication between the chamberand orifice. The upstream orifice plate 42 contains a plurality ofintake passages 51 which afford communication between the upstream faceand chamber 49. The operation is similar to that already described forthe form shown in FIGURE 1, although the venturi has an advantage thatit offers less increase in pressure drop with increases in velocity.

FIGURE 4 shows a modification in which the fluid which reaches thechamber is taken from the downstream end of the restriction. Thehousing, connector and venturi parts are constructed similarly to thosealready described in FIGURE 1, except that the upstream venturi part 13ahas no intake passages, but instead the downstream venturi part 14a hasa single intake passage 53 communicating with chamber 21. I fix a Pitottube 54 to the downstream face of the venturi part 14a communicatingwith passage 53. I position the inlet end of the Pitot tube adjacent thedownstream end of the restriction where it receives a portion of thefluid discharging from the flared outlet passage 19. This fluid flowsback through the Pitot tube and passage into chamber 21, where itsaction is similar to that already described for FIGURE 1.

FIGURE shows a series of curves which demonstrate the results of tests Iconducted with my controller constructed as shown in FIGURE 1. Theabscissae of these curves represent pressure differentials in pounds persquare inch at opposite ends of the controller, and the ordinates theresulting flow in gallons per minute. The inlet passage 17 of thiscontroller had an included angle of 14, the throat 18 a length of 4 inchand a diameter of A; inch, and the outlet passage 19 an included angleof 8. The fluid was a relatively light hydraulic oil. Curve showsresults I obtained by holding the upstream pressure constant at about500 psi. and varying the downstream pressure with a throttle valve. Thiscurve shows that the flow rate increased rapidly with increases inpressure difference until the differential reached about 150 psi. with aflow rate of about 7.25 gallons per minute, whereafter greater pressuredifferences produced no further increase in the flow rate. The velocityat the venturi throat with the limiting flow rate was about 189 fps.Similarly curves B, C and D show results I obtained with the samecontroller and fluid, but with the upstream pressure held constant at1000 psi, 1500 psi. and 2000 psi. respectively. In each instance theflow rate reached a definite limiting value which was maintainedregardless of further increases in the pressure dif ferential.

As fluid from the chamber impinges on the stream at the restriction, itcreates turbulence in the stream. I believe this turbulence isresponsible for limiting the flow rate, but I am unable to explain theaction further. The static pressure of the stream at the restriction ofcourse decreases as the velocity increases, in accordance withBernoullis well-known principle. Thus the static pressure might dropsufiiciently to approach the vapor pressure, with the result that aliquid would vaporize. The velocity of the vapor would automatically belimited to the speed at which sound travels therethrough. However, myobservation is that the velocity does not reach suflicient values toexplain the action in this manner. I obtained the curves of FIGURE 5with oil of low vapor pressure, but I have obtained similar curves withwater of much higher vapor pressure. I also find the action isindependent of the viscosity of the fluid, at least within the limits ofabout 1 to 40 centipoises. As long as the fluid is a liquid,

the limiting flow rate is proportional to the square root of theabsolute upstream of the pressure difference pressure, and the criticalvalue is about one-third the absolute upstream pressure. The limitingflow rate also is directly proportional to the cross sectional area ofthe restriction. If the fluid is a gas, the limiting flow rate of thegas reduced to standard condition is directly proportional to theabsolute upstream pressure.

I have also obtained interesting results by connecting two of mycontrollers in series and measuring pressure at the upstream end of theupstream controller, between the two controllers, and at the downstreamend of the downstream controller. Two controllers lowered the limitingflow rate only slightly as compared with a single controller. However,the resistance before the limiting flow rate was reached approximatelydoubled, as I would expect. Before the limiting fiow rate was reached,the pressure drop was divided evenly between the two controllers. Afterthis flow rate was reached, the pressure drop across the upstreamcontroller remained constant, and all additional pressure drop tookplace across the downstream controller. I actually observed a small butmeasurable decrease in flow rate with increasing pressure differentialsabove the critical value.

From the foregoing description it is seen that my invention affords acontroller of especially simple construction for effectively limitingthe rate at which fluid can flow therethrough. My controller is compact,as required for use in an oil well, and it is entirely free of movingparts likely to need maintenance. It is apparent also that I can use thebypass or" FIGURE 2 or the Pitot tube of FIGURE 4 with the orificeconstruction of FIGURE 3.

While I have shown and described certain preferred embodiments of myinvention, it is apparent that other modification may arise. Therefore,I do not wish to be limited to the disclosure set forth but only by thescope of the appended claims.

I claim:

1. A flow controller comprising a housing having upstream and downstreamends for receiving and discharging a stream of fluid, a first memberfixed in said housing and having an opening which extends therethroughand tapers toward said downstream end, a second member fixed in saidhousing between said first member and said downstream end and having anopening which extends therethrough and is aligned with said first-namedopening and flares toward said downstream end, said openings jointlydefining a venturi throat through which the stream flows at a highervelocity than through the remainder of the housing, said members havingsurfaces which face each other adjacent their outer peripheries and arespaced apart to define an annular chamber, said members also havingsurfaces which face each other between said chamber and said throat andare spaced apart a shorter distance than said first-named surfaces todefine an annular passage which furnishes communication between saidchamber and said throat throughout the circumference of the latter, andintake means furnishing communication between said chamber and saidupstream end for introducing fluid to said chamber and thence throughsaid passage into said throat to impinge on the stream in said throat,thereby creating turbulence in the stream which limits the flow ratethrough said housing to a predetermined maximum as long as the pressureon said upstream end remains constant despite loss of pressure on saiddownstream end.

2. A controller as defined in claim 1 in which said intake means is inthe form of passages which extend through said first member.

3. A controller as defined in claim 1 in which said intake means is inthe form of a bypass extending outside said housing, and said controllerincludes an adjustable valve in said bypass.

4. The combination, with a source of fluid adapted to be maintained atsubstantially constant pressure and means connected to said source towhich a stream of fluid is delivered therefrom, said means being subjectto loss of resistance which increases the pressure difference betweensaid source and said means, of a controller comprising a housing havingupstream and downstream ends connected respectively to said source andto said means to receive and discharge the fluid stream, a first memberfixed in said housing and having an opening which extends therethroughand tapers toward said downstream end, a second member fixed in saidhousing between said first member and said downstream end and having anopening which extends therethrough and is aligned with said first-namedopening and flares toward said downstream end, said openings jointlydefining a venturi throat through which the stream flows at a highervelocity than through the remainder of the housing, said members havingsurfaces which face each other adjacent their outer peripheries and arespaced apart to define an annular chamber, said members also havingsurfaces which face each other between said chamber and said throat andare spaced apart a shorter distance than said first-named surfaces todefine an annular passage which furnishes communication between saidchamber and said throat throughout the circumference of the latter, andintake means furnishing comunication between said chamber and saidupstream end for introducing fluid to said chamber and thence throughsaid passage into said throat to impinge on the stream in said throat,thereby creating turbulence in the stream which limits the flow ratethrough said housing to a predetermined maximum as long as the pressureat said source remains constant despite loss of resistance at saidfirst-named means.

5. A combination as defined in claim 4 in which the fluid is a liquid,the maximum flow rate is proportional approximately to the square rootof the absolute pressure at said source, and the maximum flow rate isreached when the difference in pressure between said source and saidfirst-named means is approximately one-third the absolute pressure atsaid source.

References Cited in the file of this patent UNITED STATES PATENTS1,112,066 Hollis Sept. 29, 1914 2,118,428 Chrisman May 24, 19382,501,593 Becker Mar. 21, 1950 2,502,602 Stresen-Reuter Apr. 4, 19502,912,821 Horak July 25, 1958

1. A FLOW CONTROLLER COMPRISING A HOUSING HAVING UPSTREAM AND DOWNSTREAMENDS FOR RECEIVING AND DISCHARGING A STREAM OF FLUID, A FIRST MEMBERFIXED IN SAID HOUSING AND HAVING AN OPENING WHICH EXTENDS THERETHROUGHAND TAPERS TOWARD SAID DOWNSTREAM END, A SECOND MEMBER FIXED IN SAIDHOUSING BETWEEN SAID FIRST MEMBER AND SAID DOWNSTREAM END AND HAVING ANOPENING WHICH EXTENDS THERETHROUGH AND IS ALIGNED WITH SAID FIRST-NAMEDOPENING AND FLARES TOWARD SAID DOWNSTREAM END, SAID OPENINGS JOINTLYDEFINING A VENTURI THROAT THROUGH WHICH THE STREAM FLOWS AT A HIGHTERVELOCITY THAN THROUGH THE REMAINDER OF THE HOUSING, SAID MEMBERS HAVINGSURFACES WHICH FACE EACH OTHER ADJACENT THEIR OUTER PERIPHERIES AND ARESPACED APART TO DEFINE AN ANNULAR CHAMBER, SAID MEMBERS ALSO HAVINGSURFACES WHICH FACE EACH OTHER BETWEEN SAID CHAMBER AND SAID THROAT ANDARE SPACED APART A SHORTER DISTANCE THAN SAID FIRST-NAMED SURFACES TODEFINE AN ANNULAR PASSAGE WHICH FURNISHES COMMUNICATION BETWEEN SAIDCHAMBER AND SAID THROAT THROUGHOUT THE CIRCUMFERENCE OF THE LATTER, ANDINTAKE MEANS FURNISHING COMMUNICATION BETWEEN SAID CHAMBER AND SAIDUPSTREAM END FOR INTRODUCING FLUID TO SAID CHAMBER AND THENCE THROUGHSAID PASSAGE INTO SAID THROAT TO IMPINGE ON THE STREAM IN SAID THROAT,THEREBY CREATING TURBULENCE IN THE STREAM WHICH LIMITS THE FLOW RATETHROUGH SAID HOUSING TO A PREDETERMINED MAXIMUM AS LONG AS THE PRESSUREON SAID UPSTREAM END REMAINS CONSTANT DESPITE LOSS OF PRESSURE ON SAIDDOWNSTREAM END.